Search engines that use link popularity to rank web sites tend to skew their results in favor of web sites that are more popular. Google uses an algorithm called PageRank that assigns a numerical weighting to each element of a hyperlinked set of documents to measure its relative importance within the set. PageRank results from voting among all other web pages about how important a web page is. A hyperlink to a page counts as a vote of support. Similarly, a web page that is linked to by many pages with high PageRank receives a high rank itself. If there are no links to a web page, there is no support for that web page.
Further, search engine rankings also influence consumer behavior. For instance, most users only click on the first result in a list of search results generaged by a search engine. Most users do not look past the first result in the list. As such, search engines that rank results with click-through popularity very soon wind up with links that are effectively permanent in the first few positions.